Experimental concept and direct OAM extraction results.^[67] (a)–(c) Schematic experimental methodology. (a) Two circularly polarized ultrashort pulses with temporal separation Δt are launched at a plasmonic vortex-generating sample. (b) The pump pulse launches SPPs at the structure edges on the sample. (c) The probe pulse interferes with the propagating SPPs and liberates photoelectrons in a 2PP process, which are then imaged with the PEEM setup. (d)–(g) Experimental TR-PEEM snapshot sequence of the rotating field of a plasmonic vortex in the revolution stage within a single optical cycle of ∼ 2.67 fs. The red dot follows a specific lobe as it rotates around the center. The yellow dashed-dotted lines serve as reference frames to emphasize the rotation. The angle between the upper two yellow lines is 36°, corresponding to 2π/₁₀ rads.